Support CTRL-E and CTRL-Y

[openjck]

From the Vim documentation:

							*CTRL-E*
CTRL-E			Scroll window [count] lines downwards in the buffer.
			The text moves upwards on the screen.
			Mnemonic: Extra lines.

							*CTRL-Y*
CTRL-Y			Scroll window [count] lines upwards in the buffer.
			The text moves downwards on the screen.
			Note: When using the MS-Windows key bindings CTRL-Y is
			remapped to redo.